Fix parameter without 'in' on clean_operations

[lucasrcosta]

The following is a valid YAML and breaks in the current code, since the param will be a dict but won't have in:

parameters:
  - in: path
    name: some_param
    required: true
    type: string
  - $ref: "#/parameters/ParamRef"

[sloria]

Build failure is unrelated to these changes. Looks good. Thanks again!